Semester 1 Topic 3 Level H – Ignite Mathematics

Task Name : Adding and Subtracting Negative Number Stories		Task Level : H (Year 7)
Semester : 1	Topic : Directed Numbers		VC Strand : Number and Place Value
Web Address : http://maths.crusoecollege.vic.edu.au/npvH
Equipment Needed : Poster Paper
Victorian Curriculum outcome : Compare, order, add and subtract integers
Task description : Students create eight stories that describe addition and subtraction of positive and negative numbers. Two should describe the addition of positive numbers; two should describe the subtraction of positive numbers; two should describe the addition of negative numbers; and two should describe the subtraction of negative numbers. Each story should contain: the written story; a picture accompanying the story; a number line describing the story; and an algorithm describing the story.
Assessment options : Photograph of poster; digital image.
Teacher notes : Money is a good way to describe these processes. If I have $5 and I gain $10, the algorithm is ⁺5 + ⁺10 = ⁺15 . However, if I have $5 and then gain a bill for $10, this can be thought of as “negative money”, and so the algorithm is ⁺5 + ^–10 = ^–5. Using this analogy, it is easy to see why if I lose a bill (perhaps the issuer recognises that it is a mistake and takes it back), then the algorithm is ⁺5 – ^–10 = ⁺15… students can see that losing a bill means that you are better off financially.